1. Field of the Invention
The present invention generally relates to an integrated micro-droplet generator and more particularly, relates to a thermal bubble type inkjet head that is equipped with a symmetrical, off-shooter heater and a method for fabricating the head.
2. Background
Since the advent of printers, and specifically for low cost printers for personal computers, a variety of inkjet printing mechanisms have been developed and utilized in the industry. These inkjet printing mechanisms include the piezoelectric type, the electrostatic type and the thermal bubble type, etc. After the first thermal inkjet printer becomes commercially available in the early 1980's, there has been a great progress in the development of inkjet printing technology.
In an inkjet printer, a liquid droplet injector is used as one of the key mechanisms. To provide a high-quality and reliable inkjet printer, the availability of a liquid droplet injector capable of supplying high-quality droplets at high-frequency and high-spacial resolution is critical.
Presently, there are two types of inkjet printers that are available in the market, the piezoelectric type and the thermal type. The thermal inkjet system, also known as thermal bubble inkjet system, thermally driven bubble system or as bubble jet system utilizes bubble to eject ink droplets out of an ink supply chamber, while piezoelectric printers utilize piezoelectric actuators to pump ink out from a reservoir chamber. The principle of operation for a thermal bubble inkjet system is that an electrical current is first used to heat an electrode to boil liquid in an ink reservoir chamber. When the liquid is in a boiling state, bubble forms in the liquid and expands and thus functioning as a pump to eject a fixed quantity of liquid from the reservoir chamber through an orifice and then forms into droplets. When the electrical current is turned-off, the bubble generated collapses and liquid refills the chamber by capillary force.
When evaluating the performance of a thermal bubble inkjet system, factors such as droplet ejection frequency, cross talk between adjacent chambers and the generation of satellite droplets are considered. Two of these performance requirements, i.e. the satellite droplets, which degrade the sharpness of the image produced and the cross talk between adjacent chambers and flow channels which decrease the quality and reliability of the inkjet system are frequently encountered. In order to improve the performance of a thermal bubble inkjet system, these drawbacks must be corrected.
It is therefore an object of the present invention to provide a thermal bubble inkjet head that does not have the drawbacks or the shortcomings of the conventional thermal bubble inkjet head.
It is another object of the present invention to provide a thermal bubble inkjet head that is equipped with a symmetrical ring-shaped heater for generating bubbles.
It is another further object of the present invention to provide a thermal bubble inkjet head that is equipped with an ink chamber.
It is yet another object of the present invention to provide a method for fabricating a thermal bubble inkjet head that is equipped with a symmetrical heater.
It is still another further object of the present invention to provide a method for fabricating a thermal bubble inkjet head that is equipped with a symmetrical heater by utilizing two separate thick photoresist deposition processes and a nickel electroplating process.